To determine the chemical and physical changes induced in the lens proteins during a hereditary cataractogenesis in the rat. The following aspects will be emphasized: 1. Quantitative determination of cysteine (yields SH) and cystine (-S-S-) by carboxymethylation, and of tryptophan by spectrophotometric and chehical modification procedures. 2. Isolation of albuminoids by differential solubilization of lens proteins and their chemical and physical characterization by amino acid analysis, U.V. spectrophotometry, acrylamide gel electrophoresis and peptide mapping. 3. Use of chaotropic agents for solubilization of lens tissue and separation of proteins by preparatory disc-gel electrophoresis, and characterization of fractionated proteins.